The present invention relates to the control of access to a shared document in a communication network of the “station-to-station” or distributed type, commonly referred to as the “peer-to-peer” topology type.
During the past few years, station-to-station networks have become an alternative to the client/server networks which have become widespread up to the present time. This is because, through their distributed architecture, station-to-station networks make it possible to share a large number of digital data between a large number of users, without for all that requiring an expensive infrastructure.
In practice, in a station-to-station network, each station fulfills the role of client and server. Thus each station can request data or a digital document from any other station in the network and the exchange of data can take place directly from one station to another.
Hereinafter, the term “document or digital data” applies both to images or digital videos, or to digital text files or the like.
Thus, in a station-to-station data exchange, each station can be both client and server.
This means that the digital data received by a client station can then be served to other users by said client station.
The digital data accessed by many persons can therefore be replicated on several machines and served by more servers.
The system therefore adapts all alone to demand and the communication storage costs are distributed between all the servers.
On the other hand, in a conventional client/server system, the data are served by a single server or by a set of machines fixed in advance.
The capacity of these conventional servers must be sized in advance, which results either in oversizings (the cost of the server is then too high) or undersizings (the data are not served sufficiently rapidly).
Another advantage of the station-to-station system is that the digital data are served directly from the machines of the users.
The storage space can therefore be considered in practice to be unlimited.
However, station-to-station networks are unstable. This is because the client devices (and consequently the server devices) connect to each other and disconnect from each other periodically on the network, thus making the presence of the data very haphazard. In addition, the addresses of the client and/or server devices are unpredictable and liable to be different at each connection.
As a result access to the contents in a communication network of the station-to-station type still constitutes a significant difficulty, since the latency for obtaining the data is no longer simply due to the time necessary for recovering the data as in the conventional client/server topology, but also the search time for a server device having these data available.
According to the topology of the station-to-station network concerned, this search phase may be not insignificant.
In the context of the invention, the context is more precisely adopted of a communication system exchanging digital data by means of digital containers of these data.
For example, the digital data are digital photographs/images which can be represented in hierarchical storage format with multiple representations (in terms of resolution and memory size).
A digital container of such data is for example a collection of digital photographs, that is to say a container of references to these images, where various sub-parts or representations can be situated on different machines in the network.
The majority of station-to-station data exchange systems are intended for exchanging public data: the whole world can access a shared data item.
The present invention is preferentially concerned with a particular context where the data exchanged are personal. It is a case for example of images or videos which a person wishes to share with his friends or family, that is to say a restricted number of users. The data are then not public.
In this context, it is necessary to have a system for restricting access to the data. A list of documents and an associated access list are grouped together in the collection. When sharing, the collection is sent to all the addressees. Each one decides to accept the collection or not. If the addressee accepts the collection, this supplements the local access list of the client machine for each of the documents contained. Likewise, for the creator of the collection, the new collection supplements the local access lists.
The control of access to the data from the client machines is based on the trust of a person who is sharing a personal data item with regard to an addressee who has received this data item: the server of the addressee must, in dealing with access to his machine and the validity of the requests, comply with the restrictions proposed by the creator of the data. However, the destination can apply a different limitation of access to the data which he has received.
A so-called hybrid station-to-station system has the particularity of comprising a permanent server (also referred to as a central server), which can serve for registering users, and controlling the connection of the client machines of these users.
For the purpose of increasing the availability of the digital data on the station-to-station network and thus promoting the broadcast service quality, the central server can also store, locally and temporarily, limited versions of personal digital data.
The Applicant has posed the problem for itself of supplying access control as well as control of the sharing and distribution of the personal documents on the central server of a hybrid station-to-station network.